Can't See Background Image on Ortho View
Background images will only be displayed in


  Camera Prespective view (Numpad 0)


Any of the Preset Orthographic views


  
  Front/Back (Numpad 1 or CtrlNumpad 1)
  Right /Left (Numpad 3 or CtrlNumpad 3)
  Top/Bottom (Numpad 7 or CtrlNumpad 7)
  


Background images will not show in perspective view. 

To switch between Perspective and Orthographic view use Numpad 5

Background images are used for reference only and will not be part of the final render.